The reason they hate the idea that it is a behavioral choice is that this reality puts the onus (that’s with an o) of their sexual preferences on themselves instead of removing the “blame” to being “born that way”, ie, blaming God.
The unconscious thought process is “if God made me this way, there’s no way He’ll hold me accountable, but if it’s a choice, and I viscerally know that it’s wrong, I know I will be judged for my choices.”
I believe homosexuals are born that way, just like all sinners. We are all born into sin of some type or another but that truth isn't the ticket punch to God's forgivness.